Method of manufacturing concrete pipe



Feb. 15, 1955 R. E. SULLIVAN 2,701,905

moo 0F munc'ruamc concns'rs PIPE Filed April 10,, 1950 3 Sheets-Sheet 1 m7 E. SML/VRM IN VHV TOR.

Feb. 15, 1955 R E. SULLIVAN 2,701,905

' METHOD OF MANUFACTURING comm PIPE Filed April 10. 1950 3 Sheets-Sheet 2 m7 6. ML/m/V,

INVENTOR.

1955 R. E. SULLIVAN METHOD or MANUFACTURING concurs PIPE Filed April 10. 1950 3 Sheets-Sheet 3 wZV/ll/lllll/II/rll/lrill/711111!!!FIIIII/l/r/r/l/fi we! 6. 5040mm a. I INVENTOR 6 United States Patent 2,101,905 METHOD or MANUFACTURING CONCRETE PIPE 'Robert E. Sullivan, Oceanside, Calif., asslgnor to Steam- Cote Corporation, a corporation of California Application April 10, 1950, Serial No. 154,997

Claims. (CL'25-154) My invention relates to reinforced concrete pipe and method of manufacture, and included in the ob ects of my invention are:

First, to provide a reinforced concrete pipe built up of concrete laminae so disposed that a dense impervious layer of high cement content constitutes the inner surface of the pipe and is present at the interfaces of the several layers, so as to provide a concrete pipe Wl'llCh 1s particularly impermeable to water or other fluids.

Second, to provide a laminated reinforced concrete pipe which is particularly strong and capable of withstanding internal pressures substantially higher than has heretofore been feasible in concrete pipe.

Third, to provide a laminated concrete coating which because of its impervious nature, may be applied to steel pipe for its protection.

Fourth, to provide a method of forming reinforced concrete pipe, wherein an atomized air-water mixture 2,101,905 Patented Feb. 15, 1955 ice 2 mandrels to be described hereinafter. Such mandrels are adapted to rotate about the axes of the supports 5 as well as about the axis of shaft 3. A conveyer 8 is provided to deliver mandrels to the turntable and to remove them therefrom.

Each mandrel structure includes a tubular mandrel 11 on which is mounted a sleeve 12 formed of rubber or flowing at high velocity and under pressure entrains a cement-sand aggregate and directs the resulting augmented mixture at high velocity against a mandrel or previous lamina in such a manner that the fines, cement, and water, combine to form a dense inner layer of h gh homogeneity and an outer more porous layer contamrng the larger particles and particularly suitable for bonding with a succeeding lamina. I Fifth, to provide a method for forming concrete pipe, wherein the inner lamina is applied to a mandrel having a rubber or rubber-like sleeve capable of being stripped from within the pipe to leave a particularly smooth mterior having a low fluid friction factor.

Sixth, to provide a laminated concrete coated metal pipe and method of manufacture; that is, a metal pipe over which is applied laminations of concrete which may include reinforcing to aid in retaining the concrete on the llVith the above and other objects in view as may appear hereinafter, reference is made to the accompanying drawings, in which:

Figure l is a perspective view illustrating the manner in which the pipe and pipe-mandrels are handled, and the method of applying the cementitious material.

Figure 2 is a fragmentary side elevational view of the spray unit.

Figure 3 through 3-3 of Figure 2, illustrating particularly one of the spray nozzles and showing in connection therewith, a control valve.

Figure 4 is a partial elevational partial sectional view of the mandrel structure on which the cementitious material is applied.

Figure 5 is an enlarged fragmentary sectional view I of the mandrel and the pipe formed thereon.

,closed within the turntable are suitable means to rotate mandrel supports 5 located at the extremities of the arms 4, said means being shown fragmentarily in Figure 4. Near the upper end of the shaft 3, other arms 6 are provided, which are provided at their extremities with roller clamps 7, adapted to receive the upper ends of is an enlarged fragmentary sectional view rubber-like material. If the pipe to be formed is the larged, as indicated by 13, .to mold the interior of the bell end of the pipe. The mandrel and sleeve rest on a base 14 which is secured by a tie rod 15 extending to the top of the mandrel and provided with a loop end 16, to facilitate its being carried by a conveyer.

Mounted at one side of the turntable 2 is a carriage 21 which includes a hopper 22 and operator's platform 23. The carriage 21 is adapted to be raised and lowered by suitable means such as hydraulic cylinder 24 and cable 25. Carried by the hopper are spray units 26, shown best in Figures 2 and 3.

Each spray unit ncludes a'body 27 adapted to be secured to the side of the hopper 22. The extended end of the body .27 is provided with a socket 28 which receives an outer nozzle 29. The outer nozzle comprises a metal tube 30 which loosely receives a'liner 31, one end of which is folded over the tube and provides a frictional fit within the socket 28. The liner is formed of rubber or rubber-like material -and protrudes beyond the tube 30. inwardly of the socket 28, the body 27 is provided with a constriction behind which is formed a chamber 32. The base end of the body is again restricted, but is provided with a bore which receives an inner nozzle 33 which projects through the chamber 32 and forms with the constriction which separates the chamber 32 from the socket 28, an annular venturi port 34. The bore of the inner nozzle is. lined with a yieldable rubber-like liner 35, the tip of which protrudes slightly beyond the inner nozzle.

The chamber 32 is connected by a supply line 36 to an air-water mixer valve 37. The mixer valve includes a body 38 having a piston 39 therein, operated by a suitable handle 40. The piston controls a central relatively large air port 41 and a smaller offset water port 42. These ports are connected respectively to a source of air and water. In the passage terminating in the water port 42 is interposed a meter valve 43. By adjustment of the meter valve the percentage of water and air introduced under given pressure conditions may be controlled. The air thoroughly atomizes the water in its passage from the valve 37 to the chamber 32 and discharges in such atomized form through the venturi port 34 at sufiicient velocity to establish a vacuum capable of drawing a cement-sand aggregate from the hopper 22. The augmented mixture then flows through the outer nozzle 29 at high velocity and intimately mixes with the air and water upon contact, so that thorough mixing occurs.

My method of forming'concrete pipe is as follows:

A mandrel 11 is placed in front of the hopper 22 so that the material discharged from the nozzles 31 thereof impinge on the mandrel. As shown in Figure 2, several nozzle units are employed, arranged in a vertical row. The carriage is moved to one extreme end of the mandrel, and while the mandrel is rotated, the

carriage is slowly moved to the other axial extremity,

causing the cementitious material to impinge upon the mandrel. If several nozzles are used, as the four shown, several layers or laminae of cementitious materal are applied. The first layer or lamina 51 of material impinges directly on the yieldable surface of the mandrel sleeve 12. It has been found that under the conditions obtained by the type of nozzle shown, the fines and cement flow past and around the larger particles of the material, with the result that the inner layer of the first lamina adjacent the mandrel sleeve is rich in cement and fines, so that after curing, a very dense and impervious inner skin is formed. It is not known whether mixture with the water actually takes place during free travel from the nozzle to the mandrel, or whether the mixture takes place between the water and the dry material at the instant of impact. In any case, the fines and water do form a-paste-like material parable to that of metal pipe.

which clings to the mandrel in sufficient quantity 'to build up an appreciable layer of material.

The second and succeeding lamina 52 is impinged in a like manner on the underlying lamina, so that the resulting pipe wall comprises a series of dense zones 53 bound intimately with a less dense underlayer. The result is a pipe structure which appears to be stronger than would be the case if the material where homogeneously mixed throughout the thickness of the pipe wall. In addition, the permeability of the pipe wall is materially less than can be accounted for by the average density of the material.

By use of several nozzles, the succeeding laminae are applied in rapid succession without any setting time between applications. If it is desired toemploy reinforcing, several laminae are first applied, for example three, as shown in Figure 5, whereupon the pipe, while still retained on the mandrel, is allowedto cure or partially cure until the surface is sufliciently strong to permit winding of the reinforcing under tension. The reinforcing is preferably in the form of steel wire and includes longitudinal reinforcing members 55 held in place by a spiral wrapped reinforcing56. After application of the reinforcing, an outside or cover layer or lamina 57 is applied. The pipe is then cured untd sufliciently strong to permit withdrawal of the mandrel. By reason of the rubber or rubber-like sleeve 12, the mandrel may be forced from within the completed pipe. The resulting pipe has a particularly smooth and void-free inner surface, so that although formed of cementitious material, has a low friction factor com- It has been found that reinforced concrete pipe made according to my method, is capable of withstanding internal pressures comparable to'that of metal pipe, in fact three-inch pipe has been tested to pressure of 800 pounds per square inch.

It has been found that a sand-cement mixture of six to one is quite satisfactory. Also it has been found that the sand-may be such as to pass through a number 8 screen. About two and one-half "gallons of water is used with each bag of cement (one cubic foot). While these proportions are believed to be optimum it is believed that substantial variation may be made if desired. The term cement as herein used is intended to designate conventional Portland or hydraulic cement.

While the original mixture may be six to one, the resulting mixture ratio on the pipe appears to be four to one or three to one. The larger particles of sand are thrown or bounce off and are quite free of cement covering, but the smaller particles or fines tend to imbed in the cement. It is believed that the pounding action of these grains play an important part in producing the desired quality of cement laminae.

The rotation of the pipe during spraying may play an important part. The optimum peripheral speed is between seventy'five and one hundred feet per minute; for example a four inch pipe would be rotated about seventy-five to one hundred R. P. M.; whereas a fifteen inch pipe would be rotated between twenty-five and thirty R. P. M.

Regardless of the cause, whether rebound due to the velocity and mass of the particles or the effect of centrifugal force it is a fact that the resulting sandcement mixture is on the average considerably richer than the original mix and that each lamina is richest in fines and cement adjacent its radially inner surface.

Reference is now directed to Figure 7. It has been found that excellent bond may be obtained on steel 4 I claim:

l. A method of manufacturing pipe, characterized by simultaneously mixing an unconsolidated mixture of dry cement and sand particles with a plurality of high-velocity ets containing atomized water'in suspension to form a plurality of streams moving in the same direction; rotating a tubular mandrel about an axis substantially at right angles to the path of the streams; directing the high velocpipe, indicated by 61, by application of cement in acity streams of moistened cement and sand mixture against axially ad acent areas of said rotating mandrel; relatively moving the streams and mandrel to position successive axial portions of the mandrel in the path of the streams as the mandrel is being rotated, whereby the streams of said mixture produce a corresponding plurality of laminations covering the mandrel; the sand content of the mixture being in excess of the sand content desired in said laminations, and comprising relatively fineand coarse particles; the moisture content being so regulated and the velocity of said streams and the speed of rotation of the mandrel and the relative axial movement of the streams and mandrel being such that a substantial percentage of the coarse sand particles rebound from the mandrel and preceding laminations, their kinetic energy being employed to impact the finer sand particles and cement into dense impervious masses.

2. A method of manufacturing pipe as set forth in claim 1, wherein: said mandrel is removed from within said laminations after at least partial curing of said cement.

3. A method of manufacturing pipe as set forth in claim 1, wherein: the innermost lamination is bonded to said simultaneously mixing an unconsolidated mixture of dry cement and sand particles with a high-velocity jet containing atomized water in suspension to form a stream; rotating a tubular mandrel about anaxis substantially at right angles to the path of the stream; directing the high velocity stream of moistened cement and sand mixture against the rotating mandrel; relatively moving the stream and mandrel to position successive axial portions of the mandrel in the path of the stream as the mandrel is being'rotated, whereby the stream of said mixture produces a lamination covering the mandrel, the sand content of the mixture being in excess of the sand content desired in said lamination and comprising relatively fine and coarse particles, the moisture content of the mixture being so regulated and the velocity of the stream and the speed of rotation of the mandrel and the relative axial movement of the stream and mandrel being such that a substantial percentage of said coarse particles rebound from the mandrel, their kinetic.

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